The invention relates to methods and apparatus for testing for the proper assembly of components of apparatus having moving parts. More particularly, the invention pertains to methods and apparatus for determining the proper assembly of automotive engine blocks, including the internal moving parts of such blocks.
While moving down an assembly line, automotive engines may be subject to assembly errors, either by human operators or by automated equipment. Traditionally, two of the most commonly encountered assembly errors for engine components are reversed piston heads and missing connecting rod bearings.
FIG. 1 depicts the cross-section of an engine block 100 showing a crankshaft 106 having a center line of rotation 104 and the connecting rod 108 and its associated piston head 110 for one cylinder 102 of the engine. If piston head 110 is installed incorrectly- that is, upside down, then head 110 will lie at an angle to the longitudinal center line of the cylinder, thereby creating a "slap" condition which is obviously detrimental to proper functioning of the engine once it is fully assembled and started. The slap condition arises from head 110 improperly contacting the cylinder wall at points 111 and 112.
Similarly, if during the assembly process , a bearing between crankshaft 106 and connecting rod 108 is omitted, connecting rod 108 and its associated piston head 110 will not operate as intended. Rather pronounced knocking vibrations will result from the connecting rod having too much "play" during its stroke, due to the absence of the bearing.
In conventional assembly processes, assembly errors such as those discussed above have been discovered either "the hard way" by starting the fully assembled engine and suffering the consequences, by use of complicated and expensive optical inspection systems, or by labor-intensive manual inspection.
Therefore, there is seen to be a need in the art for an automated, yet relatively simple method and apparatus for determining whether proper assembly of a device having moving internal parts, such as an automotive internal combustion engine, has taken place.